Occasionally the Equalizer window will randomly disappear. At that point using the Toggle Equalizer button does no good. The only fix is to restart the program or to go into Configure>Equalizer and hit the Reset button.

This time it's the Playlist window causing mischief. The Playlist randomly decided to be topmost window above all other applications on the desktop. The main interface and the equalizer windows were happy to fall to the bottom of the stack.

Zipped up the Xion data folder and happy to email it if you provide an address to send it to.